Cataract surgery often involves removing an opacified crystalline lens through phacoemulsification (PEA), and implanting an intraocular lens after the crystalline lens has been removed. Intraocular lenses include hard intraocular lenses whose optical parts are made of hard materials such as PMMA or the like, and soft intraocular lenses whose optical parts are made of soft materials such as silicon elastomer, soft acrylic, hydrogel or the like.
When inserting a hard intraocular lens, there has to be formed on the cornea or the sclera an incision substantially as wide as the diameter of the optical part of the corresponding hard intraocular lens. In contrast, a soft intraocular lens can be inserted through an incision smaller than the diameter of the optical part thereof by allowing the corresponding optical part to be folded.
An intraocular lens is preferably inserted through a small incision in order to reduce the possibilities of corneal astigmatism and infection after the surgery. In this sense, soft intraocular lenses tend to be preferred nowadays. Types of soft intraocular lens include: a soft intraocular lens having an optical part made of a soft material and supporting portions made of a hard material such as PMMA or the like (the supporting portions of this type of intraocular lens are usually two thin filamentary members); a soft intraocular lens whose optical part and supporting portions are made of a same soft material (the supporting portions of this type are usually plate members); or a soft intraocular lens employing a plurality of thin strips as supporting portions, and the like.
Further, in order to insert an intraocular lens into an eye, there has also been used a dedicated intraocular lens insertion device having a structure for introducing the intraocular lens into the eye through an elongated tube. This type of intraocular lens insertion device allows an intraocular lens to be inserted through an incision smaller than 3 mm.
Furthermore, in recent years, there has been developed a type of intraocular lens insertion device which has an intraocular lens placed therein in advance and can be packaged and stored, in order to exclude the possibilities of bacteria contamination and errors in operation at the time of handling the intraocular lens (e.g., patent document 1).
However, this type of intraocular lens insertion device may cause a supporting portion (referred to as a rear supporting portion, hereunder) arranged on a rear side with respect to a lens advancement axis to slip in between a plunger for pushing out the intraocular lens and a passage inner wall surface of the insertion device, or be tangled with the corresponding plunger, during a process of moving the intraocular lens. These problems are particularly noticeable with soft intraocular lenses employing thin filamentary members as supporting portions and intraocular lenses employing thin strips as supporting portions.
Further, this type of intraocular lens insertion device may cause the rear supporting portion to be stretched during the process of moving the intraocular lens. Accordingly, the corresponding rear supporting portion may then be left outside an eye ball at the time of performing insertion through a small incision on the eyeball, thereby requiring an additional operation for inserting such rear supporting portion into the eye ball after pushing out the intraocular lens with the plunger, and thus making the surgery troublesome.
In this sense, when using an intraocular lens insertion device to insert an intraocular lens into an eye, the motion of the rear supporting portion of the intraocular lens has to be appropriately regulated during the process of moving the intraocular lens.
In view of the aforementioned problems, there has been disclosed a device in which a clearance is formed on a front end side portion of a plunger, for allowing the rear supporting portion to be kept therein and thus preventing the same from being damaged (e.g., patent document 2). Further, there has been disclosed a device in which a rear supporting portion receiving passage for receiving the rear supporting portion is provided on a lower side portion of a plunger (e.g., patent document 3). Furthermore, there has also been disclosed a device in which the rear supporting portion is pushed up on a lump portion by means of a plunger, thereby allowing the corresponding haptic to be bended upward and eventually positioned higher than an IOL (e.g., patent document 4). Accordingly, all the devices disclosed in the aforementioned patent documents serve to reduce holding pressures applied to the rear supporting portions of intraocular lenses employing thin filaments or strips as supporting portions.